Trifluoroacetic acid → 5,6-Dihydrophenanthridine

Participants

Reaction Steps

The intermediate dihydrophenanthridine was prepared from 6-ethyl-8-fluoro-phenanthridine, (Example 40, Step b, 0.79 g, 3.48 mmol), by treatment with sodium borohydride (0.79 g, 21 mmol) and trifluoroacetic acid (1.1 mL, 14 mmol) in tetrahydrofuran (18 mL). In a separate, second step, the dihydrophenanthridine was treated with triethylamine (0.8 mL, 6 mmol) and 4-methoxy-3-methylbenzenesulfonyl chloride (0.66 g, 3.0 mmol, 2 equivalents) in dichloromethane (5 mL) according to the procedure and in the same manner as described in Example 32, Method A, Step d. The crude product was purified by flash column chromatography on silica gel, eluting with a mixture of ethyl acetate-hexane (1:19 to 3:7 gradient), to yield 6-ethyl-8-fluoro-5-[(4-methoxy-3-methylphenyl)sulfonyl]-5,6-dihydrophenanthridine as a homogeneous, white solid (0.57 g, 92% from the dihydrophenanthridine), m.p. 140° C.;

Provenance & Evidence